A children or an adult without much life experience.This manga is about people who are "Zebra", people who had lived in both light and dark.People who never experienced that may have hard time understanding characters' feeling.I will not blame the author for this because this manga is too short.It'd be better if this manga were longer so that it could go in details about character feelings and relationships. Since it's just 6 volumes of manga with more than 20 characters, you can't do anything much but to try to understand characters and their relationships by your own.If you could understand it, this manga will be very brilliant. If you think you can't understand other people feelings(especially the feelings of people who lives in the dark, people who made mistakes, people who commit crimes), you should better skip this manga since it will be a waste of your time.